1. Field
One or more embodiments of the present disclosure relate to a composite anode active material, a method of preparing the same, a lithium battery including the composite anode active material.
2. Description of the Related Technology
Small, light-weight lithium batteries with high charging and discharging capacities are available for use in portable electronic devices for information communications, such as personal data assistants (PDAs), mobile phones, and laptop computers, or electric bicycles, electric vehicles, and the like.
Lithium batteries such as lithium ion secondary batteries, may be manufactured using materials for a cathode and an anode that allow intercalation or deintercalation of lithium ions, and an organic electrolyte solution or polymer electrolyte solution disposed between the cathode and the anode.
Lithium ion secondary batteries generate electrical energy through oxidation and reduction reactions that take place during intercalation and deintercalation of lithium ions in the anode and cathode.
Lithium ion secondary batteries may use lithium metal as an anode active material, but it may form dendrites causing a short circuit and thus a high risk of failure of the battery. To overcome these shortcomings, carbonaceous materials have been often used as anode materials instead of lithium metals.
Crystalline carbonaceous materials such as natural graphite and artificial graphite, and amorphous carbonaceous materials such as soft carbon and hard carbon are available as carbonaceous materials. Amorphous carbonaceous materials may have high capacities; however, adversely are highly likely to be irreversibly altered in charging and discharging cycles. For this reason, graphite as crystalline carbonaceous material is currently in wide use.
Recently, lithium titanium oxide has been investigated as an anode active material for lithium ion secondary batteries. One such material is a lithium titanium oxide (Li4Ti5O12) having a higher operating voltage of about 1.5V relative to carbonaceous materials and a theoretical capacity of about 175 mAh/g which is only half the capacity relative to graphite as a crystalline carbonaceous material. Including lithium titanium oxide (Li4Ti5O12) as an anode active material for lithium ion secondary batteries ensures a high charging and discharging rate with nearly zero irreversible reaction, and provides high stability of the battery because it produces very low reaction heat. Although Li4Ti5O12 has a higher theoretical density of about 3.5 cc/g relative to carbonaceous materials having a theoretical density of about 2 g/cc, it is similar in capacity per volume as carbonaceous materials.
Furthermore, with the increasing use of lithium ion secondary batteries, as power sources for portable devices, electric vehicles and as large-capacity power storage devices, there is a demand for a material affording a high charging and discharging rate and long lifetime characteristics with a similar capacity per volume as carbonaceous materials as an anode active material for lithium batteries.